<p>The <code>inject</code> predicate allows you to inject JavaScript to determine if
the predicate should match or not.  The JavaScript should be a function that accepts
the request object (and optionally a logger)  and returns true or false.
See the <a href='/docs/api/injection'>injection page</a> for details.</p>

<p>The execution will have access to a node.js environment.  The following example uses
node's <code>Buffer</code> object to decode base64 to a byte array.</p>

<testScenario name='tcp inject example'>
    <step type='http'>
<pre><code>POST /imposters HTTP/1.1
Host: localhost:<%= port %>
Accept: application/json
Content-Type: application/json

{
  "port": 4555,
  "protocol": "tcp",
  "mode": "binary",
  "stubs": [<strong class='highlight1'>
    {
      "responses": [{ "is": { "data": "Zmlyc3QgcmVzcG9uc2U=" } }],
      "predicates": [{
        "inject": "function (request, logger) { logger.info('Inside injection'); return Buffer.from(request.data, 'base64')[2] &gt; 100; }"
      }]
    }</strong>,<strong class='highlight2'>
    {
      "responses": [{ "is": { "data": "c2Vjb25kIHJlc3BvbnNl" } }],
      "predicates": [{
        "inject": "request => { return Buffer.from(request.data, 'base64')[2] &lt;= 100; }"
      }]
    }</strong>
  ]
}</code></pre>
    </step>

<p>The first stub matches if the third byte is greater than 100.  The request we're
sending is an encoding <code>[99, 100, 101]:</code></p>

    <step type='exec'>
<pre><code>echo '<strong class='highlight1'>Y2Rl</strong>' | base64 --decode | nc localhost 4555</code></pre>

        <assertResponse>
<pre><code><strong class='highlight1'>first response</strong></code></pre>
        </assertResponse>
    </step>

<p>The logs will also show the injected log output.  The second predicate has to
match a request originating from localhost with the third byte less than or equal
to 100.  We're sending <code>[98, 99, 100]</code>:</p>

    <step type='exec'>
<pre><code>echo '<strong class='highlight1'>YmNk</strong>' | base64 --decode | nc localhost 4555</code></pre>

<p>...giving the response:</p>

        <assertResponse>
<pre><code>second response</code></pre>
        </assertResponse>
    </step>

    <step type='http'>
<code class='hidden'>DELETE /imposters/4555 HTTP/1.1
Host: localhost:<%= port %>
Accept: application/json</code>
    </step>
</testScenario>
